Korach son of Izhar son of Kohath son of Levi separated himself, with Dathan and Abiram, sons of Eliab, and On son of Peleth, the offspring of Reuben. (Num. 16:1)

Rav Binyamin Ze'ev Kahane, the son of Rav Meir Kahane, relates: 'Rashi comes and repeats the question asked by the sages: “Now Korach who was prudent, why did he commit this folly?” In other words, it is obvious that Korach was not some nut, but rather a “gadol” in Torah, as we will soon see. He also appreciated the greatness of Moshe Rabbeinu, as the Parasha itself testifies to, and knew that Moshe was not after the “kavod”. And so he should have known that there would be some serious Divine backlash to the steps he was taking. This being the case: “Why did he commit this folly?” And Rashi answers: “His eyes deceived him; he saw a great chain (i.e., a chain of great men) issuing from him, (viz.,) Shmuel, who weighed against Moshe and Aharon. [Korach] said: Because of him I shall be saved. And twenty-four 'watches' will arise from his son's sons, all of them prophesying through 'Ruach HaKodesh' ... [Korach] said: Is it possible that all this greatness is destined to arise from me and I shall remain silent? Therefore he associated himself to come to that prerogative: for he heard from the mouth of Moshe that all of them would perish and one would be saved, one that the Eternal One would choose, that one would be holy; he erred and applied this to himself; but he didn't see correctly, for his sons would return to G-d and that was what Moshe had seen.”
And here we must ask a great question: We are talking about a tremendous Torah giant with “Ruach HaKodesh” who was capable of seeing generations and generations into the future! How then, could a man with such great vision and prophecy walk like a blind man in an alley, unable to understand something which any thinking, logical person could understand who does not possess any special “Ruach HaKodesh”?' (The writings of Rav Binyamin Ze'ev Kahane, HY”D, Parashat Korach)

A possible explanation, by taking a look at Korach's collaborators in the rebellion, can be found in Rabbi Meir Kahane's Peirush HaMaccabee on Shemot and Isaiah:
So they got themselves up from near the dwelling of Korach, Dathan and Abiram, from all around. Dathan and Abiram went out “nitzavim” (erect) at the entrance of their tents, with their wives, children and infants (Num. 16:27).
[Chazal said regarding this:]
The expression “yetziva” (standing erect) always refers to prophecy, as it says, I saw the Lord “nitzav” (standing erect) on the Altar (Amos 9:1), and it also says, And Hashem came, “va-yityatzav” (and was present) … (1 Samuel 3:10) (Mechilta de-Rabbi Yishmael, Beshallach 3; Shirata 10)
And similarly: The expression “yetziva” (standing erect) always refers to Ruach ha-Kodesh (ibid.).That is to say, every time that the Tanach uses the expression “yetziva” (standing erect) with reference to a tzaddik, implying that he stands straight and upright and strong, stubborn and steadfast, unflinching and sure, proud and fearless, this is because G-d is with him at that time.
After all, it would otherwise be inconceivable for the term “yetziva” (standing erect) to apply to a mortal man, who is alive today and dead tomorrow, strong today yet old and feeble tomorrow. The adjective, “yatziv” (erect, firm) and the verb “nitzav” (stand erect) refer specifically to G-d, as in the verse: G-d “nitzav” (stands erect) in the Divine congregation (Psalms 82:1). And this is the reason that the Torah uses the same verb to describe Israel at Mount Sinai: “va-yityatz’vu” (and they stood erect) at the bottom of the mountain (Exodus 19:17). And similarly: You “nitzavim” (are standing erect) today, all of you, before Hashem your G-d (Deuteronomy 29:9).
And G-d uses the same verb in instructing Moses to appear before Pharaoh: Get up early in the morning, “ve-hityatzev”(and stand erect) before Pharaoh (Exodus 8:16). On the face of it, this seems puzzling: how could Moses possibly have dared to go to Pharaoh – and more than that, to stand proudly before him? – Only because G-d was with him.

However, this same verb is sometimes applied to evil people: the Torah says that Dathan and Abiram went out nitzavim (“standing erect”) (Numbers 16:27).
And the Midrash explains:
They went out reviling and blaspheming, as it says, they went out standing erect. Similarly, later on the Tanach says: And the Philistine [Goliath] would approach morning and evening, “va-yityatzev” (and he stood erect) for forty days [reviling and blaspheming](1 Samuel 17:16) (Tanchuma, Korach 8).This is because evil people arrogate to themselves the status of standing erect, which is the diametric opposite of the tzaddik:The tzaddik who has elevated himself and sanctified himself and shed his pride knows that he can succeed only in the merit of the power that G-d has nitzav (“relegated”) to him, even as he himself is a worm and not a man (Psalms 22:7). By contrast, the evil person, who is of coarse spirit and arrogant, claims that he stands erect through his own power – and more, like Dathan, Abiram, and Goliath, he blasphemes Hashem. And this is how David describes the nations: The kings of the earth “yityatz’vu” (stand erect)…against Hashem and against His anointed (Psalms 2:2), although He Who dwells in Heaven will laugh, the Lord will make fun of them (verse 4).And so at the Red Sea, Moses told the Children of Israel: “hityatz’vu” (stand erect) and see Hashem’s salvation (Exodus 14:13). More than this: if the Jewish nation will be humble, and will accept upon itself the yoke of Heaven, then no man “yityatzev” (will stand erect) before you (Deuteronomy 7:24).

G-d performed a miracle by making Aaron’s staff – a dry wooden stick – blossom, as it says Moses came to the Tent of Testimony, and behold! Aaron’s staff had flowered…flowers had come forth, and blossoms had blossomed (Numbers 17:23).G-d smashed Korach’s arrogance, and that of Dathan and Abiram, who in their arrogance knew only how to make fight and contention blossom and flourish, as the Torah says of Dathan and Abiram, behold, two Hebrew men were contending (Exodus 2:13). The Hebrew word “nitzim” (contending) connotes quarrels that sprout and blossom forth, like the “nitzanim” [blossoms] are seen in the Land (Song of Songs 2:12). In their arrogance, these men kicked against G-d and sought to aggrandize themselves; and G-d symbolized the humiliation of the arrogant and the aggrandizement of the humble and those who believe in Him by the staff, a simple wooden stick that was in the Tent of Testimony, sprouted and blossomed.
Only the humble and the modest can be great; only one who makes himself small will become truly great, while if he makes himself great, then he will shrink to the tiniest of dimensions.
And every person must believe that all his achievements and accomplishments come solely through G-d’s providence.

The prophet Ezekiel said: And all the trees of the field will know that I, Hashem, have cast down the tall tree, I have raised up the lowly tree; I have dried up the moist tree, I have cause the dried-up tree to flourish (Ezekiel 17:24).
And the Midrash interprets: “I have cast down the tall tree” – this is Korach; “I have raised up the lowly tree” – this is Aaron, as it says, “behold! Aaron’s staff had flowered”…; “I have dried up the moist tree” – these are Abimelech’s wives…; “I have caused the dried-up tree to flourish” – this is Sarah (Yalkut Shimoni, Ezekiel 357). And all of this is the keystone of faith.